Carburetor



Fb. 11, 1936. s, SMITH 2,030,331

CARBURETOR Filed Jan. 25, 1953 3 sheets-Sheet 1 I N VEN TOR.

Byff' Feb. 11, 1936. 5, C;l SMITH 2,030,331

CARBURETOR Filed Jan. 25, 1935 3 Sheets-Sheet 2 INVENTOR.

w. Q W@ ATTORNEY S. C. SMITH CARBURETOR Feb. 11, 1936.

3 sheets-sh eet 5 vFiled. Jan. 25, 1955 w ...Emmi w 1.. 1 y xnkm" x 1 ATTORNEY Patented Feb. 11, 1936 Stuyvesant C. Smith, South Bend, Ind., assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware v Application January 25, 1933, Serial No. 653,500

`9Claims.

'I'hls invention relates to carburetors for internal combustion engines, more particularly it relates to control mechanism for the carburetor, and has for its principal object the provision of 5 a mechanism actuated jointly by a thermostat and vacuum in the engine for controlling the richness of the fuel mixture as a function of temperature.

Internal combustion engines using a mixture 1'0 of liquid fuel and air require a very rich mixture to start and require that the richness of the mixture be graded down as the engine warms up to prevent stalling when the engine is idling. In the prior art ofwhich I am aware, the copending application of Hunt and Olson, Serial No. 575,025, led November 14, 1932, being an example, there is provided a control of the choke valve of the carburetor by thermostatically actuated means to grade down the richness-of .the

fuel mixture as avv function of engine tempera-- ture. J

. 4 vThe present invention, which is, broadly speaking, an improvement upon said copending application, provides a thermostat which is connected to the choke valve of the carburetor to control vthe richness of the mixture produced thereby, and provides a. vacuum actuated piston coupled to the valve and thermostat by a spring which is tensioned to oppose the tension of the thermo- 3'0' stat, this spring being adjustable so that 4the setting of the valve can be accurately controlled. The invention will be best understood from the detailed description and claims which follow, referenc'e being had to the accompanying drawings in which a. preferred embodiment of the invention is shown by way of example and in which:

Figure 1 is a ditic view, partly in section, showing the apparatus of the invention;

Figure 2 is a fragmentary view, partly in section, of a modification of the apparatus;

Figure 3 isa view similar to Figure 1 showing another modification;

Figure 4 shows the invention adapted to a particular carburetor;

ll'lgure5isaviewsimilartoliig'urelshowingl buretor I0 having a balanced choke valve I2 and a throttle I4. 'I'he -;rburetor is shown as a plain tube down draft carburetor, this type being illustrated by way of example only as the invention may be applied to other types of carburetors within the teachings of the invention. The shaft I3 of the choke valve carries a lever I5 fixed thereto and a lever I6 is xed on the shaft of the throttle. 'Ihese levers are connected by a rod 20 connected to lever I5 and coupled to lever i o I8 by a lost motion connection. As-the throttle approaches its wide open position, lever I8 operates rod 20 to crack the choke valve so that a flooded condition of the engine can be corrected. 'I'he amount that the vchoke valve is.opened is 15 governed by an adjusting nut 2|. The choke valve I2 is provided with a small poppet valve I6 of known construction to admit air for starting.

A thermostat casing 22 is mounted upon a suitable bracket 23 xed upon the intake mani- 20 fold of the engine adjacent to the carburetor, and a shaft 26 is journaled inthe casing. A thermo-responsive element 28 is xed to the shaft and wound therearound and is disposed so as to be heated by heat radiated from the exhaust 25 manifold of the engine. "Ifhe free end of the element bears against a stud 30 projecting from the casing. An arm 32 is xed upon the shaft and its freeend is connected to' the choke lever I5 by' a rod 34. When the engine is cold thermo- 30 stat 26 is tensioned to rotate lever 32 and close the choke valve and to maintainA it closed during starting.

A cylinder 36 is mounted upontheintake manifold 24 and communicates therewith through a 35 suitable port 3l. A piston 38 is tted in the cylinder and urged upwardly therein by a spring 40. A rod 4I is xed to the piston and extends through an ear 42 on lever 32' and therebeyond, the end of the rod being threaded to receive an 40 adjusting nut 44. A sleeve 45 formed on nut 44 surrounds the rod, and a spring 46 surrounds the sleeve .and bears against ear 42 and nut 44.

When it is desired to start the engine the throttle is set to starting position, that is, about 45 I one fourth open, kand the choke valve is closed by the automatic mechanism just described. The engine is cranked and as soon as it begins firing piston 38 is drawn downwardly against the tension of spring 40. Sleeve 45 engages ear 42 and' 5o moves lever 32 to crack the, choke valve so that the engine will not stall. Spring 46 is tensioned in opposition to the tension of the thermostat. As the engine warms up, the thermostat tension decreases and spring 46 moves lever 32 to open u,

thermostat 28 will have zero tension and theY choke valve will be fully opened.` As the thermostat is heated further, as it will be by heat radiated from the exhaust manifold of the engine, the end of the element moves away from bracket 30 and engages a Ysecond bracket 48. The

-thermostat is then tensioned in the opposite direction to aid spring 46 in holding the choke valve open. The particular type of thermostat shown is not new, being shown and more fully described in the copending application of S. F. Hunt, SerialNo. 647,641, filed December 16, 1932. When the engine is stopped, spring 40 raises the piston and the tension of spring 46 isreduced. As the .engine cools down, the thermostat is -retensioned and lever 32 operated thereby to close the choke valve.

The modification shown in Figure 2 is adapted for use with a carburetor having an unbalanced choke valve. In this modification the thermostat, which is housed in a casing 22, is provided with a shaft 26 upon which arm 32 is fixed as before. Rod 34 connects the arm to the choke valve. A lever 56 is fixed upon shaft 26 and carries a pin 5|. A second lever 52 is pivotally mounted upon the frame work of the mechanism and connected to the throttle by suitable means 53. When the throttle is moved to wide open position, lever 52 engages pin 5I and arm 32 is moved to open the choke valve so that a flooded conditionl of the engine may be corrected. A shaft 54 is journaled in the mechanism framework above and parallel to shaft 26. A lever 56 floats on this shaft and carries an ear 42 through which rod 4| extends. Cylinder 36 is'mounted upon the intake manifold and communicates therewith through a port as before. The cylinder carries a piston 38 which is urged upwardly by spring 4|!A and to which rod 4| is connected. A sleeve 45 surrounds the rod and a spring 46 surrounds the sleeve and bears against a nut 44 and the ear 42 as before. Lever 56 is connected to lever 58 by a link 58 to apply the tension of.

spring 46 tothe thermostat, as will presently appear. A second lever 60 floats upon shaft 54 and is connected to lever 50 bya link 62. When the choke valve is 'closed the 'pivotal connection' between link 62 and lever 50 is aligned with the median line of the link and the axis of shaft 26, to form a toggle lock for holding the valve closed. When the valve is fully opened the pivotal connection of link 62 to lever 60 aligns with the median line of the link and the axis of shaft 54 to form a toggle lock for holding the valve open.

In the operation of the device, the thermostat when cold is tensioned with more tension than is required for the proper operation of the carburetor, that tension decreasing as the engine warms up. The engine is. cranked with the choke valve closed and as soon as the engine fires,piston 38 is drawn down against the tension of spring 48. Spring 46 is tensioned tb move lever 56 counterclockwise on shaft 54 and through link 58 to break the toggle holding the valve closed. The tension of spring 46 subtracts from the tension of the thermostat and the choke valve is opened by 'the pressure difference upon its posterior and anterior faces under the control of the thermostat. The degree of opening of the valve at any particular temperature can be regulated by adjusting nut 44 to add to or subtract fromA the tension of spring 46. When the choke valve is wide open it is locked by the toggle lock. When the engine stops and cools down tension is built up in the thermostat and the toggle is broken and the valve closed.

In the modification shown in Figure 3 thermostat shaft 26 carries a multiarm lever 66 and choke valve control rod 34 is Aconnected to the free end of one of the arms. A pivoted lever 68 is^ connected `to piston 38 and provided with an ear 42 through which a rod 10 extends. The rod 10 is connected to one ofthe arms of lever 66. A sleeve surrounds the rod,r and a spring 46 surrounds the sleeve and bears against the ear and a nut 44 as before. A third arm of lever 66 carries ya pin 1I against which a lever 12 is adapted to bear. Lever 12 isconnected by rod 13 to the Ithrottle lever and the lever 12 thus moves the pin valve when the `is tensioned to hold the choke valve closed when the engine is cold. When the engine fires, piston 38 is .drawn into the cylinder and'spring 46 tensionedlto oppose the tension of the thermostat to permit the choke V.valve |2 to open under the pressure difference on itsfaces. The tension of spring 46 is adjusted by nut 44 askbefore.

In Figure 4 I have shown the invention adapted to a carburetor having a choke valve which comprises two leaves 14 which are hinged to the sidewalls of the' structure. A stud 15 is fixed in the carburetor midway between the leaves of the valve. sliding, and is urged upwardly thereonby a spring 11. Collar 16 is grooved to receive thev ends of arms 18 which are fixed on the leaves adjacent' to the hinges. Air pressure on the upper face of the leaves and vacuum on the lower faces causes the leaves to swing- 'on their hinges and the collar to move downwardly against the tension of spring 11. In the control mechanism, thermostat arm is xed on the thermostat shaft and connected by a rod 8| to a pivoted lever 82 which carries an ear-42. Piston 38 is urgedupwardly in cylinder 36 `by spring 40 and carries rod 4| which extends through the ear and is threaded toreceive nut 44 by which spring 46 and sleeve 45 are held on the rod. A bell crank lever 84 is pivoted adjacent to lever 82 and-carries an ear 85 through which rod 86 slidably projects. One end of this rod is pivotally connected to lever 82 and the other end is threaded to receive a nut 81. A spring 88 surrounds the vrod and bears against ear and nut 81. A crank arm 80 is journaled in the carburetor casing and connected to lever 84 by a rod 9|. The free end of arm 86 bears against one of the leaves of the choke valve.

When the engine is cold and not running, thermostat 28, which is of the type shown in copending application of S. F. Hunt, Serial No. 647,641, above referred to, vis tensioned to raise arm 80 and thereby rotate lever 82 clockwise on its pivot. Spring 88 is tensioned to rotate arm 84 and with it arm 90 to close the choke valve. The thermostat is tensionedsufliciently to keep the valve closed during starting of the engine. When'the engine fires, piston 38fisdrawn downwardly in the cylinder against the tension of spring 40 and .spring 461s tensioned to oppose the thermostat A collar 16 is mounted on the stud for.

sion the eective force holding the valve closed is insumcient to resist the air pressure on it. The thermostat is arranged to decrease its tension as the engine warms up and the valve opens wider, being fully opened when the engine reaches normal operating temperature. As the valvefopens, tension is built up in spring 15. When the engine is stopped spring 40 raises piston 38 to decrease the tension in spring 46 and as the engine cools tension is built up in the thermostat and functions to rotate arm 90 to close the valve with the aid of spring 15. Adjustments of the choke setting are made by adjusting nuts 44 and 81."

In the embodiment of the invention shownin Figure 5, the shaft of thermostat carries a cam 92 uponv which is mounted a pin 93. A lever 52 is pivotally mounted adjacent to the cam and connected to the throttle of the carburetor by suitable means 53. When the throttleis movedto wideopen position, lever 52 engages and moves cam 92 to partially open the choke valve. y A shaft 94 is journaled in the casing of the mechanism and carries a lever 96 which is fixed thereto and carries a roller 95 that engages the cam. A second lever 98 is fixed upon shaft 94 and connected by rod 34 to the choke valve I2. A lever 91 oats upon shaft 94 and is connected to piston 38. Spring 40 urges piston 38 upwardly to move lever 91 counterclockwise on shaft 94n` Lever 96 carries an ear 99 which overhangs lever 91 so that the tension o f spring 40 is applied to lever 98 to hold the chokevalve closed.

When the engine is cold, shaft 26 is urged counterclockwise by the tension in the thermostat. A shoulder |01 on the cam strikes roller 95 to apply the thermostat tension to lever 98 to aid in keeping the choke valve closed while the engine Qis being cranked. Immediately the engine fires piston 38 is drawn downwardly against spring 40 and lever 91 is moved away fromvear 99 so that the tension of spring 40 is removed from the valve and it is partially opened against the tension of the thermostat by the diiference of air pressure on its faces. As the thermostat is heated cam 92 is rotated clockwise. Roller 95 rides over cam surface |00.

valve. When the enginereaches normal operpending application of S. F. Hunt, Serial No. 'f

653,518, flledJanuary 25, 1933. When the engine is shut down, spring 40 raises piston 38 and closes the choke valve as soon as the tension in thermostat 28 rotates cam 92 back so that roller `95 engages surface |00. In many V-type engines the intake manifolds and -carburetor are located on top of the engine and the exhaust manifolds are outside and under the cylinders. In an arrangement of this kind the thermostat of the control mechanism cannot be located `suiliciently close to the exhaust manlfold to permit it to'be operated by heat radiated therefrom. In Figures 6 yand 7 I have showna modincation of the invention adapting it to an" engine of this type. In this arrangement a casing |02 is mounted upon the boss |03 on tlieair horn of the carburetor in which choke valve shaft I3 is journaled. A vcylinder |04 projects from the thermostat element 28 toV move lever .96 counterclockwise and thereby open the choke bottom of this casing and is connected by a pipe |05 to the intake manifold of the engine. A stdve |06 is placed over the exhaust manifold'of the engine and connected to the casing by a pipe |01 so that hot air will be conducted to the casing.

Shaft I3 projects through the casing, and is fixed to and wound around the shaft.V A piston 38 fits in the cylinder and carries a rod I I0 having a bent end over which the free end of the thermostat ls hooked. A lever |08 floats on shaft I3 and the bent end of rod I|0 extends through and is. guided by the lever. A spring 40 ts in cylinder |04 and urges piston 38 upwardly to tension the thermostat so as to hold the choke valve closed when the engine is cold. A valve ||2 floats upon shaft'I3 and is connected to thermostat element 28 by a suitable clamp II3.

When the engine is not running and is cold. piston 38 is at the top of the cylinder and the thermostat is tensioned to hold the choke valve closed. Immediately the engine-fires, piston 38 is drawn into the cylinder against the tension of spring 40 `and the effective tension holding the valve closed is reduced to permit the valve to partially open. As the engine warms up, heat from the exhaust manifold heats stove |06 and hot air passes through pipe |01 into casing |02 to heat the thermostat. The casing is closed by a cover I I4 which has a central opening into which the end of shaft I3 projects and throughA which air escapes from the casing. Thermostat 28 loses tension as it is heated and with this loss of tension.. valve I2 is permitted to open more nearly wide open. Preferably the thermostat will be adjusted so that the valve will be wide open when the engine reaches its normal operating temperature. Further heating of the thermostat raises the hooked end'of the element off of rod I|0 and the element can move without damage to itself or tothe casing. 'I'his movement of the element carries valve II2 across the opening of pipe |01 into the casingl to block off the heat therefrom. When the engine is stopped spring 40 raises piston 38. As the thermostat cools, its hooked end is reengaged with rod IIO and the element is tensioned to close the valve. Valve II2 is moved to unblock pipe |01 and the apparatus is in readiness for another operation.

In Figures 1 to 5 inclusive I have shown the control mechanism as a separate unit mounted ajacent to the carburetor to simplify the figures. but it should be understood that the control mechanism may be included -as `an integral part o'f the carburetor within the teachings of the inl. vention. Throughout the figures parts which are not materially different in construction and function bear the same reference numerals.

Subject matter disclosed but not claimed herein is being claimed in my copending application Serial `No. 41,439, tiled September 20, 1935.

WhileI have illustrated and described a prefen-ed embodiment of'the invention, I have done 4 so `by way of example only as there are many modincations and adaptations that can be made by one skilledin the art within the teachings of the invention.

Whatisclaimed is:

1. A control mechanism for an internal combustion engine carburetor having a choke valve xed on a shaft that is journaled in and projects from the carburetor, comprising a casing xed upon the carburetor, a cylinder projecting from the casing, a piston -in the cylinder, a rod on the piston,"a thermostat connected between the shaft and rod and tensioned to rotate the shaft to close the valve when the engine is cold, said cylinder being connected to the engine and the piston actuated thereby to move the rod and reduce the tension of the thermostat when the engine hres, a stove on a heated portion of the engine, a duct connecting the stove to the casing to conduct heat thereto, and a valve floating on said shaft and connected to the thermostat and moved thereby to block said duct and regulate the amount .of heat admitted to the casing. f

2. In a carburetor having a. choke valve and a throttle, a shaft for the choke valve, a thermostatic spring operatively connected to the shaft to rotate the same, a casing enclosing the thermostatic spring, means for conveying heat to said casing, a cylinder having one end communicating with said casing and its other end connected to a source of variable pressure, and a piston in said cylinder applied to the thermostatic spring to vary the tension thereof.

3. In a carburetor, a throttle, an unbalanced choke valve mounted on a shaft, a bimetallic spring connected to said shaft to rotate the same, a casing enclosing said spring, a conduit for conveying heated gases to the casing, and a pressure-responsive member having one surface subject to the pressure in the casing and another surface subject to the suction posterior to' the throttle, said pressure-responsive member being so related to the spring that movement of the pressure-responsive member varies the tension of the spring.

4. The invention defined in claim 3, wherein a spring associated with the pressure responsive member opposes the force of said suction.

5. In a carburetor, a throttle, a pressure-responsive choke valve mounted on a shaft, a thermostatic spring of spiral form connectedto said shaft to rotate' the same, a casing enclosing the thermostatic spring, a conduit for conveying heated air to the casing, a cylinder communicating with the casing, and a piston therein having one face subject to the pressure in the casing and its opposite face subjected to pressures posterior to the throttle,'said piston being so related to the spring that movement of the piston will vary the tension of the spring.

6. In a carburetor for an internal combustion engine, a throttle, a pressure-responsive choke valve mountedl on a shaft, a thermostatic spring connected to said shaft to yieldinglyurge the choke valve toward closed position at low temperatures, a casing xed to the outerwall of the carburetor and enclosing the thermostatic spring, a conduit for conveying heated gases from a heated portion of the engine tothe casing, a conduit leading from the casing to a point posterior to the throttle. and means for varying the force exerted by the thermostatic spring on the choke valve comprising a pressure-responsive member in said last mentioned conduit subject to the varying pressures therein, and applied to the thermostatic spring by an overrunning connection.

7. In a carburetor for an internal combustion engine, a throttle, a pressure-responsive choke valve mounted on-a shaft,l a spiral bimetallic spring connected to said shaft to yieldingly urge the choke valve toward closed position at low temperatures, a casing fixed to the o'uter wall of the carburetor and enclosing the thermostatic spring, \a conduit for conveying heat from a heated portion of the engineto the casing, a second conduit leading from the casing to a source of valve suction, and means for varying the force exerted by the thermostatic spring on the choke valve comprisinga piston in said second conduit applied to the outer end of the thermostatic spring by an overrunning connection.

8. In a carburetor for an internal combustion engine, an air inlet passage, an induction passage, a throttle valve controlling the induction passage, an unbalanced choke valve controlling the air inlet passage, temperature responsive means `controlling the choke valve and adapted to move the choke valve in the closing direction at low temperatures, a casing carried by the walls of the air inlet passage and enclosing said temperature responsive means, means including a conduit to convey heated gases from a heated portion of the engine to the interior of the casing, means including a conduit interconnecting the casing and the induction passage posterior to the throttle valve, and means including a pressure responsive member in said last mentioned conduit subject to varying pressures therein for varying the force exerted by the temperature responsive means on the choke valve.

19. In a carburetor for an internal combustion engine, an induction passage, an air inlet passage communicating with the induction passage, a throttle valve-controlling the induction passage. an unbalanced pressure responsive choke valve controlling the air inlet passage, a casing fixed to the outer walls of the air inlet passage, a choke shaft journalled in the walls of the air inlet passage and projecting into said casing, temperature responsive means in the casing and operably connected to the choke shaft to modify the position of the choke valve in accordance with the temperature of theV engine, means including a conduit to convey heated gases from the engine to the casing, means including a conduit interconnecting the casing and the induction passage beyond the throttle valve and a pressure responsive member in the conduit to vary the force exerted on the 

